Thermally tolerant perpendicular magnetic anisotropy coupled elements for spin-transfer torque switching device

ABSTRACT

Perpendicular magnetic anisotropy (PMA) type magnetic random access memory cells are constructed with a composite PMA layer to provide a magnetic tunnel junction (MTJ) with an acceptable thermal barrier. A PMA coupling layer is deposited between a first PMA layer and a second PMA layer to form the composite PMA layer. The composite PMA layer may be incorporated in PMA type MRAM cells or in-plane type MRAM cells.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and is a continuation ofU.S. patent application Ser. No. 13/571,406, entitled “ThermallyTolerant Perpendicular Magnetic Anisotropy Coupled Elements ForSpin-Transfer Torque Switching Device,” filed on Aug. 10, 2012, and U.S.provisional patent application No. 61/537,778 in the names of CHEN etal., filed Sep. 22, 2011, each of the foregoing incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to Magnetic Tunnel Junction(MTJ) devices. More specifically, the present disclosure relates toincreasing thermal stability of PMA type MTJ devices.

BACKGROUND

Unlike conventional random access memory (RAM) chip technologies, inmagnetic RAM (MRAM) data is not stored as electric charge, but isinstead stored by magnetic polarization of storage elements. The storageelements are formed from two ferromagnetic layers separated by atunneling layer. One of the two ferromagnetic layers, which is referredto as the fixed layer or pinned layer, has a magnetization that is fixedin a particular direction. The other ferromagnetic magnetic layer, whichis referred to as the free layer, has a magnitization direction that canbe altered to represent either a “1” when the free layer magnetizationis anti-parallel to the fixed layer magnitization or “0” when the freelayer magnetizaiton is parallel to the fixed layer magnitization or viceversa. One such device having a fixed layer, a tunneling layer, and afree layer is a magnetic tunnel junction (MTJ). The electricalresistance of an MTJ depends on whether the free layer magnitization andfixed layer magnitization are parallall or anti-parallel with eachother. A memory device such as MRAM is built from an array ofindividually addressable MTJs.

To write data in a conventional MRAM, a write current, which exceeds acritical switching current, is applied through an MTJ. The write currentexceeding the critical switching current is sufficient to change themagnetization direction of the free layer. When the write current flowsin a first direction, the can be placed into or remain in a first state,in which its free layer magnetization direction and fixed layermagnetization direction are aligned in a parallel orientation. When thewrite current flows in a second direction, opposite to the firstdirection, the MTJ can be placed into or remain in a second state, inwhich its free layer magnetization and fixed layer magnetization are inan anti-parallel orientation.

To read data in a conventional MRAM, a read current may flow through theMTJ via the same current path used to write data in the MTJ. If themagnetizations of the MTJ's free layer and fixed layer are orientedparallel to each other, the MTJ presents a resistance that is differentthan the resistance the MTJ would present if the magnetizations of thefree layer and the fixed layer were in an anti-parallel orientation. Ina conventional MRAM, two distinct states are defined by two differentresistances of an MTJ in a bitcell of the MRAM. The two differentresistances represent a logic “0” and a logic “1” value stored by theMTJ.

Bitcells of a magnetic random access memory may be arranged in one ormore arrays including a pattern of memory elements (e.g., MTJs in caseof MRAM). STT-MRAM (Spin-Transfer-Torque Magnetic Random Access Memory)is an emerging nonvolatile memory that has advantages of non-volatility,comparable speed. to eDRAM (Embedded Dynamic Random Access Memory),smaller chip size compared to eSRAM (Embedded Static Random AccessMemory), unlimited read/write endurance, and low array leakage current.

BRIEF SUMMARY

According to an aspect of the present disclosure, a magnetic tunneljunction (MTJ) is configured with a reference layer, a tunnel barrierlayer and a composite perpendicular magnetic anisotropy (PMA) layerincluding a first PMA layer, a second PMA layer, and a PMA couplinglayer between the first PMA layer and the second PMA layer. According tothis aspect, the tunnel barrier layer is configured between thereference layer and the composite PMA layer.

Other aspects of the present disclosure include a method of constructinga perpendicular MTJ. The method includes depositing a reference layer,depositing a tunnel barrier layer and depositing a compositeperpendicular magnetic anisotropy (PMA) layer. Depositing the PMA layerincludes depositing a first PMA layer, depositing a second PMA layer,and depositing a PMA coupling layer between the first PMA layer and thesecond PMA layer. In this aspect, the tunnel barrier layer is depositedbetween the reference layer and the composite PMA layer.

In another aspect, a magnetic tunnel junction (MTJ) has means for fixingmagnetization in a first layer, and means for providing tunnelingmagnetoresistance (TMR) in a second layer. The apparatus also has meansfor increasing perpendicular magnetic anisotropy (PMA) in a compositelayer. The composite layer includes a first means for increasing PMA, asecond means for increasing PMA, and a means for coupling the firstmeans for increasing PMA and the second means for increasing PMA.

This has outlined, rather broadly, the features and technical advantagesof the present disclosure in order that the detailed description thatfollows may be better understood. Additional features and advantages ofthe disclosure will be described below. It should be appreciated bythose skilled in the art that this disclosure may be readily utilized asa basis for modifying or designing other structures for carrying out thesame purposes of the present disclosure. It should also be realized bythose skilled in the art that such equivalent constructions do notdepart from the teachings of the disclosure as set forth in the appendedclaims. The novel features, which are believed to be characteristic ofthe disclosure, both as to its organization and method of operation,together with further objects and advantages, will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following description taken in conjunction with theaccompanying drawings.

FIG. 1 is a cross-sectional diagram of a magnetic tunnel junction (MTJ)structure according to aspects of the present disclosure.

FIG. 2 is a cross-sectional diagram of a magnetic tunnel junction (MTJ)structure according to aspects of the present disclosure.

FIG. 3 is a cross-sectional diagram of a magnetic tunnel junction (MTJ)structure according to aspects of the present disclosure.

FIG. 4 is process flow diagram illustrating a method of increasingthermal stability in PMA type MRAM cells according to aspects of thepresent disclosure.

FIG. 5 is a block diagram showing an exemplary wireless communicationsystem in which an aspect of the disclosure may be advantageouslyemployed.

FIG. 6 is a block diagram illustrating a design workstation used forcircuit, layout, and logic design of a semiconductor component accordingto one aspect.

DETAILED DESCRIPTION

In one category of MRAM cells, a direction of polarization of the freelayer and the reference layer of a magnetic tunnel junction (MTJ) isparallel to the plane of the respective layer. Such memory cells arereferred to as having in-plane magnetic anisotropy or longitudinalmagnetic anisotropy (LMA) The direction of magnetic polarization of MRAMcells with in-plane magnetic anisotropy is provided by constructingmemory cells with an elongated shape, such as an ellipse. The elongatedshape provides pole locations at each end for the magnetic moment totend toward or away from.

In another category of MRAM cells, the direction of polarization of thefree layer and reference layer of an MTJ is perpendicular to the planeof the respective layer. Such memory cells are referred to as havingperpendicular magnetic anisotropy (PMA). The direction of magneticpolarization in a layer of a PMA type MRAM cell is inherentlydirectional, i.e., perpendicular to the layer. Therefore the PMA typeMRAM cells can have a symmetric shape, such as a circular shape, thatcan be more easily fabricated than elongated in-plane MRAM cells.

Circular shaped PMA type MRAM cells have a smaller area than elongatedin-plane MRAM cells and therefore may facilitate the development of moredeeply scaled memory devices. Also, because the switching current of anMRAM cell is proportional to its area. PMA type MRAM cells may consumeless power than in-plane type MRAM cells.

The polarization of the free layer and reference layer corresponds tothe magnetic moments in the materials of corresponding layers. Onechallenge to the development of PMA type MRAM is presented by a tendencyof magnetic moments in thin films to align along the film layer so thatat least a component of the magnetic moment stays mostly in the layer.This tendency which is referred to as “in-plane magnetic anisotropy” canbe overcome by application of a strong perpendicular magneticanisotropy. One way to apply a strong perpendicular magnetic anisotropyis to use a material that exhibits very strong crystalline anisotropyand has a net magnetic moment that is perpendicular to the plane of thethin film layer. The net perpendicular magnetic moment of such acrystalline material may be stronger than the in-plane magneticanisotropy. However, materials that exhibit strong crystallineanisotropy are not very compatible with existing CMOS (complementarymetal oxide semiconductor) fabrication processes.

CoFeB is a material that is compatible with CMOS processing and iscommonly used for in-plane type MRAM cells. For example, the free layerof an in-plane type MRAM cell is usually a 2 nm thick layer of CoFeB.CoFeB does not exhibit strong crystalline anisotropy and/or surfaceanisotropy so the orientation of magnetization in the material tends tostay in the film layer die to the demagnetizing field. However, it hasbeen observed that the in-plane anisotropy of CoFeB may be overcome bydecreasing the film thickness and increasing iron content. By using avery thin layer of CoFeB, film properties that are usually dominated bythe surface anisotropy of the film are instead dominated by bulkcrystalline anisotropy of the film. Such a very thin layer of CoFeBlayer used in combination with an MgO barrier layer has been observed toexhibit PMA.

The thermal barrier of an MRAM cell that is constructed with such a verythin layer of CoFeB is undesirably low because the thermal barrier isbased on the volume of the memory cell. For example, a thermal barrierof about 40 kT has been observed in such PMA type memory cellsconstructed with a very thin layer of CoFeB. This value is much lowerthan a desired thermal barrier of about 60 kT, which would be sufficientto ensure data retention in a large scale memory array.

Switching current of perpendicular MTJs can be significantly reducedbecause perpendicular MTJs can be patterned into a circular shape andthereby MTJ size can be decreased in comparison to the use ofelliptically-patterned MTJs for in-plane MTJs to have sufficient shapeanisotropy. However, the switching current density (J_(c)) ofperpendicular MTJs with a very thin CoFeB free layer tends to increasebecause such films have a high damping constant (α), a parameter whichcontributes directly to the switching current density J_(c). Becauseswitching current is switching current density J_(c) times MTJ area,increased switching current density J_(c) offsets switching currentreduction from decreased MTJ area.

According to aspects of the present disclosure, a relatively thick layerof CoFeB may be used so the damping constant is not substantiallyincreased. The CoFeB layer disclosed herein can exhibit PMA even thoughit does not have the very thin construction observed to exhibit PMA, asdescribed above. Also because of the increased thickness, the describedlayers provide an increased volume that is sufficient to provide anacceptable thermal barrier.

According to aspects of the present disclosure, the effect of in-planeanisotropy may be overcome so that the thickness of the CoFeB layer canbe increased without allowing the magnetic moments to align in the planeof the layer. According to one aspect, the in-plane anisotropy isovercome by adding layers to the memory cell that can apply aperpendicular magnetic anisotropy, (K_(u)) in the thicker CoFeB layer.

In one example, a relatively thick CoFeB free layer is provided. Withoutapplication of an additional perpendicular magnetic anisotropy, in-planeanisotropy in the relatively thick layer would cause the magneticmoments of the layer to stay in the film plane. According to aspects ofthe present disclosure, an assist layer that can be perpendicularlymagnetized is added to the stack of layers along with the thick CoFeBlayer in an MRAM cell. According to an aspect of the disclosure, theassist layer may be a very thin layer of CoFeB which can beperpendicularly magnetized. The assist layer may be coupled to the freelayer by providing a PMA coupling layer between the assist layer and thefree layer.

According to aspects of the present disclosure, the assist layerprovides the additional interfacial anisotropy that is perpendicular tothe free layer to overcome the in-plane anisotropy in the relativelythick layer. The additional free layer thickness that is provided bythis configuration also provides sufficient volume, which results in anacceptable thermal barrier.

Aspects of the present disclosure provide a method for increasingthermal stability without increasing switching current of PMA type MRAMcells made with CoFeB. In one example, the thermal barrier (E_(b)) of a20 Å thick layer of CoFeB coupled to an assist layer in a 40 nm×40 nmMRAM cell is estimated to be about 47 kT. This is a substantialimprovement compared to the thermal barrier, E_(b), of about 29 kT thatis estimated for a very thin layer of CoFeB that exhibits PMA. Inaddition to providing an acceptable thermal barrier, this exampleprovides an improved damping constant, α, and a corresponding switchingcurrent that is comparable to that observed using only the very thinlayer of CoFeB to achieve PMA.

FIG. 1 is a cross-sectional diagram of an arrangement of layers of arepresentative magnetic tunnel junction (MTJ) structure 102 according toan aspect of the disclosure. The MTJ structure 102 includes a fixed PMAreference layer 104 and a tunnel barrier layer 106 deposited on the PMAreference layer 104. The PMA reference layer 104 may be a single layerof PMA-CoFeB, PMA-FeB, PMA-CoFe, FePt, FePd, or RE-TM alloy, forexample. Alternatively, the PMA reference layer 104 may be a multi-layercombination of Co and Pt, Co and Pd, or Co and Ni, for example. The PMAreference layer 104 may also be a synthetic anti-ferromagnetic (SAF)material composition, anti-ferromagnetic or synthetic anti-ferromagneticmaterials such as CoFeB (and/or CoFe)/Ru/CoFeB (and/or CoFe),CoCrPt/Ru/CoFeB, (Co/Pt MLs)/Ru/CoFeB,PMA-multilayer/Ru/PMA-multilayer/CoFeB (and/or CoFe). The PMA referencelayer 104 may also be a composite anti-ferromagnetic (AF)/SAF layer, forexample. The tunnel barrier layer 106 may be MgO. A bottom free layer108 is deposited on the tunnel barrier layer 106. The bottom free layer108 may be a layer of PMA-CoFeB that has a thickness of less than about20 Å, or may be a layer of PMA-FeB, for example. A top free layer 112 isdeposited over the bottom free layer 108, The top free layer 112 may beanother layer of PMA-CoFeB that has a thickness of less than about 20 Åor may be a layer of PMA-FeB or PMA-CoFe, for example.

A PMA coupling layer 110 is deposited between the bottom free layer 108and the top free layer 112. The PMA coupling layer 110 may be a layer ofRu or Cr that provides a strong interlayer coupling between the bottomfree layer 108 and the top free layer 112. Alternatively the PMAcoupling layer 110 may be a layer of Cu, Pd or Pt that provides weakindirect interlayer coupling between the bottom free layer 108 and thetop free layer 112. The PMA coupling layer 110 may also be a layer ofthin metal such as Ta, Ti, Al or Hf, for example, or a thin-insulatorsuch as MgO, TaOx, TiOx, HfOx or AlOx that provides interlayer couplingor magnetostatic coupling between the bottom free layer 108 and the topfree layer 112. A PMA promotion layer 114 is deposited over the top freelayer 112. The PMA promotion layer 114 may be a back end of line (BEOL)thermal cycle tolerant material such as MgO or AlOx with low electricalresistance*area (RA), Ru, Ru/MgO, Ta/MgO, AlOx/MgO, MgO/AlOx, Cr,Cr/MgO, Pd, Pd/MgO, Pt, or Pt/MgO. A cap layer 116 or hardmask may bedeposited over the PMA promotion layer 114.

Alternatively, according to one aspect of the present disclosure (notshown) the PMA promotion layer 114 may be deposited between the bottomfree layer 108 and the top free layer 112 instead of depositing the PMAcoupling layer 110 between the bottom free layer 108 and the top freelayer 112.

FIG. 2 is a cross-sectional diagram of an arrangement of layers of arepresentative magnetic tunnel junction (MTJ) structure 202 according toanother aspect of the disclosure. The MTJ structure 202 includes a fixedPMA reference layer 204 and a tunnel barrier layer 206 deposited on thePMA reference layer 204. The PMA reference layer 204 may be a singlelayer of PMA-CoFeB, PMA-CoFe, FePt, FePd or RE-TM alloy, for example.Alternatively, the PMA reference layer 204 may be a multi-layercombination of Co and Pt, Co and Pd, or Co and Ni, for example. The PMAreference layer 204 may also be a synthetic anti-ferromagnetic (SAF)material composition, anti-ferromagnetic or synthetic anti-ferromagneticmaterials such as CoFeB (and/or CoFe)/Ru/CoFeB (and/or CoFe),CoCrPt/Ru/CoFeB, (Co/Pt MLs)/Ru/CoFeB. The PMA reference layer 204 mayalso be a composite anti-ferromagnetic (AF)/SAF layer, for example. Thetunnel harrier layer 206 may be MgO.

A free layer 208 is deposited on the tunnel barrier layer 206. The freelayer 208 may be a layer of PMA-CoFeB or PMA-FeB that has a thickness ofless than about 20 Å, for example. A thermal stability enhancement layer212 having PMA material with high energy barrier (K_(u)V) is depositedover the free layer 208. The thermal stability enhancement layer 212 maybe a layer of PMA-CoFeB or may be a layer of PMA-CoFe with high K_(u)Vfor example, which may be tuned by varying its thickness or compositionor by a PMA promotion layer.

A PMA coupling layer 210 is deposited between the free layer 208 andthermal stability enhancement layer 212. The PMA coupling layer 210 maybe a layer of Ru, Cr or thin Ta that provides a strong interlayercoupling between the free layer 208 and the thermal stabilityenhancement layer 212. A PMA promotion layer 214 is deposited over thethermal stability enhancement layer 212. The PMA promotion layer 214 maybe a back end of line (BEOL) thermal cycle tolerant material such as MgOor AlOx with low RA, Ru, Ru/MgO, Ta/MgO, AlOx/MgO, MgO/AlOx, Cr, Cr/MgO,Pd, Pd/MgO, Pt or Pt/MgO. A cap layer 216 or hardmask may be depositedover the PMA promotion layer 214.

FIG. 3 is a cross-sectional diagram of layers of a representativemagnetic tunnel junction (MTJ) structure 302 according to another aspectof the disclosure. The MTJ structure 302 includes a longitudinalmagnetic anisotropy (LMA) fixed reference layer 304 and a tunnel barrierlayer 306 that is deposited on the LMA reference layer 304. The LMAreference layer 304 may be an AF/SAF multilayer such as PtMn/(CoFeand/or CoFeB)/Ru/(CoFeB and/or CoFe). The tunnel barrier layer 306 maybe MgO. An LMA free layer 308 is deposited on the tunnel barrier layer306. The LMA free layer 308 may be a layer LMA-CoFeB or other LMAcomposite. A spacer layer 309 of Ta, Ru, Cu, Cr or a thin-insulator suchas MgO, or AlOx may be deposited over the LMA free layer 308.

A bottom PMA switching assistance layer 311 is deposited over the LMAfree layer 308 and/or the spacer layer 309. The bottom PMA switchingassistance layer 311 may be a layer of PMA-CoFeB that has a thickness ofless than about 20 Å,for example. A top PMA switching assistance layer313 is deposited over the bottom PMA switching assistance layer 311. ThePMA switching assistance layer 313 may be another layer of PMA-CoFeBthat has a thickness of less than about 20 Å or may be a layer ofPMA-CoFe, for example.

A PMA coupling layer 312 is deposited between the bottom PMA switchingassistance layer 311 and the top PMA switching assistance layer 313. ThePMA coupling layer 312 may be a layer of Ru or Cr that provides a stronginterlayer coupling between the bottom PMA switching assistance layer311 and the top PMA switching assistance layer 313. Alternatively, thePMA coupling layer 312 may be a layer of Cu, Pd or Pt that provides weakindirect interlayer coupling between the bottom PMA switching assistancelayer 311 and the top PMA switching assistance layer 313. The PMAcoupling layer 312 may also be a layer of thin metal such as Ta, Ti, Alor Hf, for example, or a thin-insulator such as MgO, TaOx, TiOx, HfOx orAlOx that provides interlayer coupling or magnetostatic coupling betweenthe bottom PMA switching assistance layer 311 and the top PMA switchingassistance layer 313.

A PMA promotion layer 314 is deposited over the top PMA switchingassistance layer 313. The PMA promotion layer 314 may be a back end ofline (BEOL) thermal cycle tolerant material such as MgO or AlOx with lowRA, Ru, Ru/Mgo, Ta/MgO, AlOx/MgO, MgO/AlOx, Cr, Cr/MgO, Pd, Pd/MgO, Ptor Pt/MgO. A cap layer 316 or hardmask may be deposited over the PMApromotion layer 314.

Alternatively, according to one aspect of the present disclosure (notshown) the PMA promotion layer 314 may be deposited between the bottomPMA switching assistance layer 311 and the top PMA switching assistancelayer 313 instead of depositing the PMA coupling layer 312 between thebottom PMA switching assistance layer 311 and the top PMA switchingassistance layer 313.

The two PMA switching assistance layers 311, 313 of the MTJ structure302, which are coupled by a PMA coupling layer 312, reduce switchingcurrent density of the longitudinal magnetic anisotropy (LMA) free layer308.

In one configuration, an MTJ includes means for fixing magnetization ina first layer, means for providing tunneling magnetoresistance (TMR) ina second layer, and means for increasing perpendicular magneticanisotropy (PMA) in a composite layer. In this configuration, thecomposite layer includes a first means for increasing PMA, a secondmeans for increasing PMA, and a means for coupling the first means forincreasing PMA and the second means for increasing PMA. Thisconfiguration may also include means for promoting PMA in a fourth layercoupled to the composite layer.

Referring to FIG. 1, the means for fixing magnetization may be thePMA-Reference Layer 104, for example. The means for providing TMR may bethe Tunnel Barrier layer 106, for example. The means for increasing PMAmay be a composite layer including the bottom free layer 108 being thefirst means for increasing PMA, the top free layer 112 being the secondmeans for increasing PMA and the PMA coupling layer 110 being the meansfor coupling the first means for increasing PMA and the second means forincreasing PMA. The means for promoting PMA may be the PMA promotionlayer 114, for example.

Although specific means have been set forth, it will be appreciated bythose skilled in the art that not all of the disclosed means arerequired to practice the disclosed configurations. Moreover, certainwell known means have not been described, to maintain focus on thedisclosure.

FIG. 4 is a process flow diagram illustrating a method of constructing aperpendicular MTJ. The method includes depositing a reference layer inblock 402, depositing a tunnel barrier layer in block 403 and depositinga composite PMA layer in block 404. The tunnel barrier layer isdeposited between the reference layer and the composite PMA layer.Depositing the composite PMA layer in block 404 includes depositing afirst PMA layer in block 406, depositing a second PMA layer in block 408and depositing a PMA coupling layer between the first PMA layer and thesecond PMA layer in block 410.

FIG. 5 is a block diagram showing an exemplary wireless communicationsystem 500 in which an aspect of the disclosure may be advantageouslyemployed. For purposes of illustration, FIG. 5 shows three remote units520, 530, and 550 and two base stations 540. It will be recognized thatwireless communication systems may have many more remote units and basestations. Remote units 520, 530, and 550 include IC devices 525A, 525Cand 525B that include the disclosed MRAM. It will be recognized thatother devices may also include the disclosed MRAM, such as the basestations, switching devices, and network equipment. FIG. 5 shows forwardlink signals 580 from the base station 540 to the remote units 520, 530,and 550 and reverse link signals 590 from the remote units 520, 530, and550 to base stations 540.

In FIG. 5, remote unit 520 is shown as a mobile telephone, remote unit530 is shown as a portable computer, and remote unit 550 is shown as afixed location remote unit in a wireless local loop system. For example,the remote units may be mobile phones, hand-held personal communicationsystems (PCS) units, portable data units such as personal dataassistants, GPS enabled devices, navigation devices, set top boxes,music players, video players, entertainment units, fixed location dataunits such as meter reading equipment, or other devices that store orretrieve data or computer instructions, or combinations thereof.Although FIG. 5 illustrates remote units according to the teachings ofthe disclosure, the disclosure is not limited to these exemplaryillustrated units. Aspects of the disclosure may be suitably employed inmany devices which include MRAM.

FIG. 6 is a block diagram illustrating a design workstation used forcircuit, layout, and logic design of a semiconductor component, such asthe MRAM disclosed above. A design workstation 600 includes a hard disk601 containing operating system software, support files, and designsoftware such as Cadence or OrCAD. The design workstation 600 alsoincludes a display 602 to facilitate design of a circuit 610 or asemiconductor component 612 such as MRAM. A storage medium 604 isprovided for tangibly storing the circuit design 610 or thesemiconductor component 612. The circuit design 610 or the semiconductorcomponent 612 may be stored on the storage medium 604 in a file formatsuch as GDSII or GERBER. The storage medium 604 may be a CD-ROM, DVD,hard disk, flash memory, or other appropriate device. Furthermore, thedesign workstation 600 includes a drive apparatus 603 for acceptinginput from or writing output to the storage medium 604.

Data recorded on the storage medium 604 may specify logic circuitconfigurations, pattern data for photolithography masks, or mask patterndata for serial write tools such as electron beam lithography. The datamay further include logic verification data such as timing diagrams ornet circuits associated with logic simulations. Providing data on thestorage medium 604 facilitates the design of the circuit design 610 orthe semiconductor component 612 by decreasing the number of processesfor designing semiconductor wafers.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. A machine-readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a memory and executed by a processor unit. Memory may beimplemented within the processor unit or external to the processor unit.As used herein the term “memory” refers to types of long term, shortterm, volatile, nonvolatile, or other memory and is not to be limited toa particular type of memory or number of memories, or type of media uponwhich memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or code on a computer-readable medium.Examples include computer-readable media encoded with a data structureand computer-readable media encoded with a computer program.Computer-readable media includes physical computer storage media. Astorage medium may be an available medium that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can include RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, orother medium that can be used to store desired program code in the formof instructions or data structures and that can be accessed by acomputer; disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andblu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

In addition to storage on computer readable medium, instructions and/ordata may be provided as signals on transmission media included in acommunication apparatus. For example, a communication apparatus mayinclude a transceiver having signals indicative of instructions anddata. The instructions and data are configured to cause one or moreprocessors to implement the functions outlined in the claims.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the technologyof the disclosure as defined by the appended claims. For example,relational terms, such as “above” and “below” are used with respect to asubstrate or electronic device. Of course, if the substrate orelectronic device is inverted, above becomes below, and vice versa.Additionally, if oriented sideways, above and below may refer to sidesof a substrate or electronic device. Moreover, the scope of the presentapplication is not intended to be limited to the particularconfigurations of the process, machine, manufacture, composition ofmatter, means, methods and steps described in the specification. As oneof ordinary skill in the art will readily appreciate from thedisclosure, processes, machines, manufacture, compositions of matter,means, methods, or steps, presently existing or later to be developedthat perform substantially the same function or achieve substantiallythe same result as the corresponding configurations described herein maybe utilized according to the present disclosure. Accordingly, theappended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

What is claimed is:
 1. A magnetic tunnel junction (MTJ) comprising: areference layer; a composite perpendicular magnetic anisotropy (PMA)layer including a first PMA layer, a second PMA layer, and a PMAcoupling layer between the first PMA layer and the second PMA layer; anda tunnel barrier layer between the reference layer and the composite PMAlayer.
 2. The MTJ of claim 1, further comprising: a PMA promotion layercoupled to the composite PMA layer.
 3. The MTJ of claim 1, in which atleast one of the first PMA layer and the second PMA layer is CoFeB. 4.The MTJ of claim 3, in which at least one of the first PMA layer and thesecond PMA layer comprises a thickness of about less than 20 Å.
 5. TheMTJ of claim 1, in which at least one of the first PMA layer and thesecond PMA layer comprises a thermal stability enhancement layer.
 6. TheMTJ of claim 1, in which the reference layer comprises a PMA referencelayer.
 7. The MTJ of claim 1, further comprising: a longitudinalmagnetic anisotropy (LMA) free layer between the tunnel barrier layerand the composite PMA layer; and a spacer layer between the LMA freelayer and the composite PMA layer, wherein the reference layer comprisesa LMA reference layer.
 8. The MTJ of claim 1, integrated in at least oneof a mobile phone, a set top box, a music player, a video player, anentertainment unit, a navigation device, a computer, a hand-heldpersonal communication systems (PCS) unit, a portable data unit, and afixed location data unit.
 9. A method of constructing a perpendicularMTJ, comprising: depositing a reference layer; depositing a compositeperpendicular magnetic anisotropy (PMA) layer including a first PMAlayer, a second PMA layer, and a PMA coupling layer between the firstPMA layer and the second PMA layer; and <depositing a tunnel barrierlayer between the reference layer and the composite PMA layer.
 10. Themethod of claim 9, further comprising integrating the MTJ into at leastone of a mobile phone, a set top box, a music player, a video player, anentertainment unit, a navigation device, a computer, a hand-heldpersonal communication systems (PCS) unit, a portable data unit, and afixed location data unit.
 11. A magnetic tunnel junction (MTJ)comprising: means for fixing magnetization in a first layer; means forproviding tunneling magnetoresistance (TMR) in a second layer; and meansfor increasing perpendicular magnetic anisotropy (PMA) in a compositelayer, the composite layer including a first means for increasing PMA, asecond means for increasing PMA, and a means for coupling the firstmeans for increasing PMA and the second means for increasing PMA. 12.The MTJ of claim 11, further comprising: means for promoting PMA in afourth layer coupled to the composite layer.
 13. The MTJ of claim 11, inwhich at least one of the first means for increasing PMA and the secondmeans for increasing PMA comprises CoFeB.
 14. The MTJ of claim 13, inwhich at least one of the first means for increasing PMA and the secondmeans for increasing PMA comprises a thickness of about less than 20 Å.15. The MTJ of claim 11, in which at least one of the first means forincreasing PMA and the second means for increasing PMA comprises athermal stability enhancement layer.
 16. The MTJ of claim 11, in whichthe means for fixing magnetization comprises a PMA reference layer. 17.The MTJ of claim 11, further comprising: means for providinglongitudinal magnetic anisotropy (LMA) between the means for providingtunneling and the means for increasing PMA; and means for spacingbetween the means for providing LMA and the means for increasing PMA, inwhich the means for fixing magnetization comprises a LMA referencelayer.
 18. The MTJ of claim 11, integrated in at least one of a mobilephone, a set top box, a music player, a video player, an entertainmentunit, a navigation device, a computer, a hand-held personalcommunication systems (PCS) unit, a portable data unit, and a fixedlocation data unit.
 19. A method of constructing a perpendicular MTJ,comprising steps of: depositing a reference layer; depositing acomposite perpendicular magnetic anisotropy (PMA) layer including afirst PMA layer, a second PMA layer, and a PMA coupling layer betweenthe first PMA layer and the second PMA layer; and depositing a tunnelbarrier layer between the reference layer and the composite PMA layer.20. The method of claim 19, further comprising a step of integrating theMTJ into at least one of a mobile phone, a set top box, a music player,a video player, an entertainment unit, a navigation device, a computer,a hand-held personal communication systems (PCS) unit, a portable dataunit, and a fixed location data unit.